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Fish Bulletin No. 84. A Racial Study of the Pacific Mackerel, Pneumatophorus diego

  • Author(s): Roedel, Phil M
  • et al.
Abstract

The Pacific mackerel (Pneumatophorus diego) is one of the more important commercial fishes found in California waters. It is fished intensively off Southern California, the great bulk of the catch being delivered to canneries located at Los Angeles and Long Beach Harbors and at Newport Beach. Landings at San Diego are erratic, though appreciable quantities have been delivered there in past years. Small amounts of mackerel are caught off Central California, but over 95 percent of the state-wide catch is made between Point Conception and the Mexican border.

The Southern California mackerel canning industry started in 1928, but demand was limited until 1933. Since that time, a virtually unlimited market has existed but the total catch has fluctuated widely and the trend has been downward since 1936. About 130,000,000 pounds were landed in the Los Angeles-Newport Beach area during the best season, 1935–1936, and some 32,000,000 pounds during the worst season, 1950–1951.

Mackerel have been taken from the Gulf of Alaska south and into the Gulf of California. They are uncommon north of Monterey Bay but are very abundant off Southern California and off much of the Pacific Coast of Baja California. Their presence in the Gulf of California was not demonstrated until 1939, and nothing is known of the magnitude of the population found there.

The early life history is fairly well known. Eggs and larvae up to 11 mm. have been described. Spawning appears largely confined to inshore waters less than 100 fathoms in depth; both eggs and larvae have been collected along the Pacific Coast from Southern California to Cape San Lucas and into the eastern portion of the Gulf of California a distance of about 250 miles. Surface water temperatures ranged from 59 degrees to 75 degrees F. at stations where eggs were collected. The spawning season is known to extend from January through August, and apparently starts earlier in the Gulf than it does along the Pacific coast. Limited surveys from Point Conception to Monterey Bay failed to produce any evidence of spawning, but juveniles have been captured near Monterey.

Mackerel seldom exceed a length of 40 cm. and a weight of two pounds. The largest specimen known was 630 mm. total length and weighed 6.36 pounds.

An extensive tagging program revealed that mackerel from as far north as Oregon and as far south as central Baja California eventually reached the Southern California fishing grounds.

Recent studies have shown that age may be determined accurately through the fifth year from otolith readings. The commercial catch in recent seasons has been dependent largely on fish one to three years old and the fish do not mature until their second or third year. The future of the fishery is, consequently, not bright, and the magnitude of the catch is and probably will remain a function of spawning success from year to year.

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